1. The Field of the Invention
The present invention relates generally to methods of voltage regulation and filtering for integrated circuits used in transceivers and transponders used in fiber-optic communications.
2. The Relevant Technology
Digital data can be efficiently propagated through a fiber-optic cable using light signals from light emitting diodes or lasers. To send data on a fiber-optic cable, the data is typically converted from electronic data generated by computers to optical data that can be propagated onto the fiber-optic cable. When data is received from a fiber-optic cable, the data is converted from optical data to electronic data so that it can received by a computer.
To convert electronic data to optical data for transmission on a fiber-optic cable, a transmitting optical subassembly (TOSA) is often used. A TOSA uses the electronic data to drive a laser diode or light emitting diode to generate the optical data. When optical data is converted to electronic data, a receiving optical subassembly (ROSA) is used. The ROSA has a photo diode that, in conjunction with other circuitry, converts the optical data to electronic data. Because most computers both transmit and receive data, most computers need both a TOSA and a ROSA to communicate through fiber-optic cables. A TOSA and ROSA can be combined into an assembly generally referred to as a transceiver or a transponder.
Transceivers and transponders commonly include at least one integrated circuit (IC). Referring to FIG. 1, a transceiver or transponder module 105 is commonly mounted on a line card 120 and receives regulated power supply voltages at industry standard IC voltages from a power supply module 140 coupled to it via a backplane 130. Examples of industry standard IC voltages include 1.8 V, 3.3 V, and 5 V.
The voltage from the power supply module 140 is regulated at the power supply module 140 to within a specified tolerance. However, at the line card 120 there may be significant noise in the voltage received from the power supply module 140 through the backplane 130. This noise may be cause by noise generated at the power supply module 140 or noise coupled by the backplane 130 into the line card 120. Power supply modules commonly used are switching power supplies. Switching power supplies regulate voltage output by rapidly switching a power source on and off. This rapid switching generates noise that may be transmitted to devices powered by the switching power supply such as the line card 120. Alternatively, the backplane 130 may act as an antenna that channels noise into the line card 120.
High frequency transceiver and transponder modules increasingly include integrated circuits that are sensitive to noise. However, it is difficult to provide adequate noise filtering because filters capable of providing the requisite noise filtering drop too large a voltage for the transceiver or transponder module 105 to function properly or at all.